This invention relates generally to gearboxes and more particularly to clean checks for closed gearboxes used in gas turbine engines.
A gas turbine engine used to propel an aircraft in flight includes a compressor that provides pressurized air to a combustor where the air is mixed with fuel and ignited for generating hot combustion gases. These gases flow downstream to one or more turbines that extract energy therefrom to power the compressor via a shaft and to produce thrust to propel the aircraft.
Aircraft engines ordinarily include a number of accessory devices, such as fuel pumps, lubrication pumps, generators and control units, which are driven by the core engine. This is typically accomplished by an accessory drive train that includes an inlet gearbox, a radial drive shaft, a transfer gearbox, a horizontal drive shaft, and an accessory gearbox. During manufacture and assembly, the gearboxes can become contaminated with metallic particles such as steel shot peen debris. If such a contaminated gearbox is installed on an engine, it is possible that the contaminants could migrate through the engine's lubrication system to other engine components such as bearings. Accordingly it is important that gearboxes installed on engines are contaminant free to preclude the possibility of bearing or other component failures.
Efforts to produce contaminant free gearboxes typically include subjecting the gearbox piece parts to a cleaning and clean check process prior to final assembly. Clean checks of such parts conventionally use an alcohol-based fluid to remove any contaminants that my be present on the parts. Such efforts are not always fully successful because additional contamination can occur during final assembly. Thus, it would be helpful to perform a clean check on the gearbox after final assembly. However, some gearboxes, particularly the accessory gearbox, are “closed gearboxes” in that they are completely closed to the exterior environment. Performing a final assembly clean check on a closed gearbox using a standard alcohol-based fluid will lead to dry spots internal to the gearbox and subsequent corrosion in the gearbox.
Accordingly, there is a need for a system and method to perform clean checks on closed gearboxes after final assembly that will not lead to internal dry spots.